.el-carousel__item:nth-child(1n) {
    background: url("../../assets/image/lun2.jpg");
}

.el-carousel__item:nth-child(2n) {
    background: url("../../assets/image/lun1.png");
}

.el-carousel__item:nth-child(3) {
    background: url("../../assets/image/lun3.jpg");
}